STEP 1Make the soup: Heat the oil in a pressure cooker over high heat. Add the onions and sauté until soft, about 3 minutes. Add the garlic and sauté 1 more minute. Add the remaining ingredients, seal the pressure-cooker lid, and bring the cooker to high pressure. Reduce the heat just enough to maintain high pressure and cook for 8 minutes. Release pressure using the quick-release method and carefully remove lid.
STEP 2Puree the soup: Transfer the soup in batches to a blender or food processor and blend until smooth. Serve hot.